MINERAL NANOFILLERS OBTAINED VIA KRYOGENIC DEZAGGREGATION METHOD.
Janowska G., Rybinski P., Slusarski L., Institute of Polymers, L/ódz
Technical University (Poland).
Activity of fillers toward polymers depends mainly on sizes of their
particles, a value of specific area and surface energy. During
manufacturing of fillers, particularly of high activity their primary
particles undergo aggregation, because of very high surface energy.
Fillers are usually introduced into polymer matrices during mechanical
mixing. However even in field of very high shear stresses complete
dezaggregation could not be achieved. In our laboratory a cryogenic
method of hydrophilic, mineral fillers dezaggregation has been
elaborated. It is based on the following assumptions. During
aggregation of primary particles empty voids inside aggregates are
formed. They could be disclosed and their sizes calculated on the
basis of gas adsorption measurements. Typically they are of an order
of a few nanometers. They are accessible to water vapour particles. In
the first step of our procedure we introduced water into the nanopores
of silica or silicates and after that have frozen all the system. As
was expected owing an increase of water volume during freezing
dezaggregation of fillers particles occured. However it was detected a
reaggregation of a filler primary particles during evaporation of
adsorbed water at elevated temperature. To avoid reaggregation it was
necessary to apply an appropriate intercalating agent. In such a
manner nanoparticles of fillers of the size below 50 nm could be
obtained. It was demonstrated their activity toward polymers, much
higher as compared to the original fillers.
The work was supported by the State Committee for Scientific Research,
Grant No. PBZ/KBN-013/T08/39